Atomistic simulation of nanomechanical properties of Alzheimer’s Aβ(1–40) amyloid fibrils under compressive and tensile loading

In addition to being associated with severe degenerative diseases, amyloids show exceptional mechanical properties including great strength, sturdiness and elasticity. However, thus far physical models that explain these properties remain elusive, and our understanding of molecular deformation and failure mechanisms of individual amyloid fibrils is limited. Here we report a series of molecular dynamics simulations, carried out to analyze the mechanical response of two-fold symmetric Aβ(1–40) amyloid fibrils, twisted protein nanofilaments consisting of a H-bonded layered structure. We find a correlation of the mechanical behavior with chemical and nanostructural rearrangements of the fibril during compressive and tensile deformation, showing that the density of H-bonds varies linearly with the measured strain. Further, we find that both compressive and tensile deformation is coupled with torsional deformation, which is manifested in a strong variation of the interlayer twist angle that is found to be proportional to both the applied stress and measured strain. In both compression and tension we observe an increase of the Young's modulus from 2.34 GPa (for less than 0.1% strain in compression and 0.2% strain in tension), to 12.43 GPa for compression and 18.05 GPa for tension. The moduli at larger deformation are in good agreement with experimental data, where values in the range of 10–20 GPa have been reported. Our studies confirm that amyloids feature a very high stiffness, and elucidate the importance of the chemical and structural rearrangements of the fibrils during deformation.     

Activation tagging using the En-I maize transposon system in Arabidopsis

A method for the generation of stable activation tag inserts was developed in Arabidopsis using the maize (Zea mays) En-I transposon system. The method employs greenhouse selectable marker genes that are useful to efficiently generate large populations of insertions. A population of about 8,300 independent stable activation tag inserts has been produced. Greenhouse-based screens for mutants in a group of plants containing about 2,900 insertions revealed about 31 dominant mutants, suggesting a dominant mutant frequency of about 1%. From the first batch of about 400 stable insertions screened in the greenhouse, four gain-in-function, dominant activation-tagged, morphological mutants were identified. A novel gain-in-function mutant called thread is described, in which the target gene belongs to the same family as the YUCCA flavin-mono-oxygenase that was identified by T-DNA activation tagging. The high frequency of identified gain-in-function mutants in the population suggests that the En-I system described here is an efficient strategy to saturate plant genomes with activation tag inserts. Because only a small number of primary transformants are required to generate an activation tag population, the En-I system appears to be an attractive alternative to study plant species where the present transformation methods have low efficiencies.     

Genotypic diversity of oscillatoriacean strains belonging to the genera Geitlerinema and Spirulina determined by 16S rDNA restriction analysis

Genotypic diversity of several cyanobacterial strains mostly isolated from marine or brackish waters, belonging to the genera Geitlerinema and Spirulina, was investigated by amplified 16S ribosomal DNA restriction analysis and compared with morphological features and response to salinity. Cluster analysis was performed on amplified 16S rDNA restriction profiles of these strains along with profiles obtained from sequence data of five Spirulina-like strains, including three representatives of the new genus Halospirulina. Our strains with tightly coiled trichomes from hypersaline waters could be assigned to the Halospirulina genus. Among the uncoiled strains, the two strains of hypersaline origin clustered together and were found to be distant from their counterparts of marine and freshwater habitat. Moreover, another cluster, formed by alkali-tolerant strains with tightly coiled trichomes, was well delineated.     

The WD40-Repeat Proteins NFC101 and NFC102 Regulate Different Aspects of Maize Development through Chromatin Modification

The maize (Zea mays) nucleosome remodeling factor complex component101 (nfc101) and nfc102 are putative paralogs encoding WD-repeat proteins with homology to plant and mammalian components of various chromatin modifying complexes. In this study, we generated transgenic lines with simultaneous nfc101 and nfc102 downregulation and analyzed phenotypic alterations, along with effects on RNA levels, the binding of NFC101/NFC102, and Rpd3-type histone deacetylases (HDACs), and histone modifications at selected targets. Direct NFC101/NFC102 binding and negative correlation with mRNA levels were observed for indeterminate1 (id1) and the florigen Zea mays CENTRORADIALIS8 (ZCN8), key activators of the floral transition. In addition, the abolition of NFC101/NFC102 association with repetitive sequences of different transposable elements (TEs) resulted in tissue-specific upregulation of nonpolyadenylated RNAs produced by these regions. All direct nfc101/nfc102 targets showed histone modification patterns linked to active chromatin in nfc101/nfc102 downregulation lines. However, different mechanisms may be involved because NFC101/NFC102 proteins mediate HDAC recruitment at id1 and TE repeats but not at ZCN8. These results, along with the pleiotropic effects observed in nfc101/nfc102 downregulation lines, suggest that NFC101 and NFC102 are components of distinct chromatin modifying complexes, which operate in different pathways and influence diverse aspects of maize development.     

Focusing Narrowly or Broadly Attention When Judging Categorical and Coordinate Spatial Relations: A MEG Study

We measured activity in the dorsal system of the human cortex with magnetoencephalography (MEG) during a matching-to-sample plus cueing paradigm, where participants judged the occurrence of changes in either categorical or coordinate spatial relations (e.g., exchanges of left versus right positions or changes in the relative distances) between images of pairs of animals. The attention window was primed in each trial to be either small or large by using cues that immediately preceded the matching image. In this manner, we could assess the modulatory effects of the scope of attention on the activity of the dorsal system of the human cortex during spatial relations processing. The MEG measurements revealed that large spatial cues yielded greater activations and longer peak latencies in the right inferior parietal lobe for coordinate trials, whereas small cues yielded greater activations and longer peak latencies in the left inferior parietal lobe for categorical trials. The activity in the superior parietal lobe, middle frontal gyrus, and visual cortex, was also modulated by the size of the spatial cues and by the type of spatial relation change. The present results support the theory that the lateralization of each kind of spatial processing hinges on differences in the sizes of regions of space attended to by the two hemispheres. In addition, the present findings are inconsistent with the idea of a right-hemispheric dominance for all kinds of challenging spatial tasks, since response times and accuracy rates showed that the categorical spatial relation task was more difficult than the coordinate task and the cortical activations were overall greater in the left hemisphere than in the right hemisphere.     

EV20, a Novel Anti-ErbB-3 Humanized Antibody,Promotes ErbB-3 Down-Regulation and Inhibits Tumor Growth In Vivo

ErbB-3 (HER-3) receptor is involved in tumor progression and resistance to therapy. Development of specific inhibitors impairing the activity of ErbB-3 is an attractive tool for cancer therapeutics. MP-RM-1, a murine monoclonal antibody targeting human ErbB-3, has shown anticancer activity in preclinical models. With the aim to provide novel candidates for clinical use, we have successfully generated a humanized version of MP-RM-1. The humanized antibody, named EV20, abrogates both ligand-dependent and ligand-independent receptor signaling of several tumor cell types, strongly promotes ErbB-3 down-regulation, and efficiently and rapidly internalizes into tumor cells. Furthermore, treatment with EV20 significantly inhibits growth of xenografts originating from prostatic, ovarian, and pancreatic cancers as well as melanoma in nude mice. In conclusion, we provide a novel candidate for ErbB-3-targeted cancer therapy.     

Sonic Hedgehog Carried by Microparticles Corrects Angiotensin II-Induced Hypertension and Endothelial Dysfunction in Mice

Microparticles are small fragments of the plasma membrane generated after cell stimulation. We recently showed that Sonic hedgehog (Shh) is present in microparticles generated from activated/apoptotic human T lymphocytes and corrects endothelial injury through nitric oxide (NO) release. This study investigates whether microparticles bearing Shh correct angiotensin II-induced hypertension and endothelial dysfunction in mice. Male Swiss mice were implanted with osmotic minipumps delivering angiotensin II (0.5 mg/kg/day) or NaCl (0.9%). Systolic blood pressure and heart rate were measured daily during 21 days. After 7 day of minipump implantation, mice received i.v. injections of microparticles (10 µg/ml) or i.p. Shh receptor antagonist cyclopamine (10 mg/kg/2 days) during one week. Angiotensin II induced a significant rise in systolic blood pressure without affecting heart rate. Microparticles reversed angiotensin II-induced hypertension, and cyclopamine prevented the effects of microparticles. Microparticles completely corrected the impairment of acetylcholine- and flow-induced relaxation in vessels from angiotensin II-infused mice. The improvement of endothelial function induced by microparticles was completely prevented by cyclopamine treatment. Moreover, microparticles alone did not modify NO and O₂ ^{. -} production in aorta, but significantly increased NO and reduced O₂ ^{. -} productions in aorta from angiotensin II-treated mice, and these effects were blocked by cyclopamine. Altogether, these results show that microparticles bearing Shh correct angiotensin II-induced hypertension and endothelial dysfunction in aorta through a mechanism associated with Shh-induced NO production and reduction of oxidative stress. These microparticles may represent a new therapeutic approach in cardiovascular diseases associated with decreased NO production.